Over the course of a 10-year follow-up period, the safety profile of Etanercept remained consistent with previous studies conducted on juvenile idiopathic arthritis and was aligned with the established safety profile. Furthermore, efficacy results were also consistent with Etanercept's profile, as deciphered from an eight-year, open-label extension of the phase 3b, 2-year CLIPPER study (CLIPPER 2).

Investigators sought to determine the effectiveness and safety of Etanercept focused on people diagnosed with juvenile idiopathic arthritis. Participants diagnosed with extended oligoarticular arthritis (2-17 years old), enthesitis-related arthritis, or psoriatic arthritis (each 12-17 years old) and who had previously received at least one dose of Etanercept (0.8 mg/kg/week; maximum 50 mg) in the CLIPPER study were eligible for the CLIPPER2 study.

The major outcome of the study was incidence of malignancy. Percentages of subjects attaining juvenile idiopathic arthritis American College of Rheumatology (ACR) 30/50/70/90/100 criteria, ACR inactive disease criteria, and clinical remission based on ACR criteria or Juvenile Arthritis Disease Activity Score (JADAS) scores ≤1 were the effectiveness evaluations. Of the initial 127 CLIPPER participants, 109 (86%) proceeded to the CLIPPER2 study, with 55 subjects having extended oligoarticular arthritis, 31 having enthesitis-related arthritis, and 23 having psoriatic arthritis.

Among them, 99 (78%) remained on active treatment. A total of 84 participants (66%) concluded the 120-month follow-up, with 32 (25%) still receiving active treatment. Only one case of malignancy (Hodgkin's illness in an eighteen-year-old patient having extended oligoarticular arthritis who had been managed with Methotrexate for eight years) was witnessed. No active tuberculosis or deaths occurred during the study period.

The incidence rates of treatment-emergent adverse events excluding infections and injection site reactions declined from 193 (173.81) events per 100 patient-years in Year 1 to 9 (27.15) events per 100 patient-years in Year 10. Both treatment-emergent infections and serious infections also declined. Overall, 127 (45%) participants achieved juvenile idiopathic arthritis ACR50 responses starting from Month 2 onwards, while 33% (n=42) and 27% (n=34) volunteers achieved JADAS and ACR clinical remission, respectively.

Etanercept treatment for around ten years exhibited a good tolerability profile and had consistency with the known safety profile. People who remained on active treatment experienced a durable response. Consequently, the benefit-risk assessment of Etanercept in these specific categories of juvenile idiopathic arthritis remained favorable. The findings of the CLIPPER2 study provide valuable insights into the extended use of Etanercept and its continued efficacy and safety, offering hope for the long-term management of juvenile idiopathic arthritis in affected children and adolescents.